This invention relates to a valve opening mechanism which is distinct from conventional valve opening mechanisms in that it is constituted so as to be capable of opening an engine valve with suitable timing by the means of a rocker arm.
The compression pressure release type of engine braking, which is constituted so that it releases pressure within a combustion chamber that has been raised by the movement of pistons through the opening of an exhaust valve in the proximity of top dead center compression, and magnifies engine braking power by diminishing the energy that drives the pistons downward in an expansion stroke, is generally known.
FIGS. 1 through 3 represent examples of the conventional compression pressure release type of engine braking. In FIG. 1, the number 1 identifies the cylinder, 2 the combustion chamber, 3 the piston, 4 the exhaust valve, and 5 the exhaust port, respectively, and they are configured so that the base extremity is thrown upward by a push rod 6 and both exhaust values 4 are pushed downward and opened through the use of the cross head by the tip of an inclining exhaust rocker arm 7, and exhaust gas is scavenged from the combustion chamber 2 toward the exhaust port 5.
Then, when both exhaust values 4 are pushed downward and opened through the use of the cross head 8 by the tip of the above-mentioned exhaust rocker arm 7, the tip of the above-mentioned exhaust rocker arm 7 pushes downward on the master piston 12 provided in the upper portion of the housing 11, a separate slave piston 14 in the upper part of the housing 11 is driven downward by the generation of pressure in the oil line 13 which protrudes into the interior of the above-mentioned housing 11 and, through the use of an actuator pin 15 installed on one side of the cross head 8, an exhaust valve 4 on one side is positioned so that it can be pushed downward independently by the said slave piston 14.
Namely, through the action of the master piston 12 in a separate cylinder 1 that constitutes an exhaust stroke, a cross linkage coinciding with the stroke timing is established by the oil line 13 between the slave piston 14 of the cylinder 1 and the master piston 12 such that the slave piston 14 in the cylinder 1 which is in proximity to top dead center compression is driven, and it is designed in such a way that operating oil 18 (engine oil) is supplied through the use of a solenoid valve 16 and a control valve 17, which constitutes a means of supplying operating oil that switches back and forth between the sustaining and release of oil pressure in the said oil line 13.
At this point, the solenoid valve 16 effects the supply of operating oil 18 by means of a control signal 20 from a control device 19, and the control valve 17 functions as a check valve so that oil pressure in the above-mentioned oil line 13 is sustained when the solenoid valve 16 is in a open state, and also serves to release oil pressure in the above-mentioned oil line 13 when the solenoid valve 16 is in a closed state.
Namely, it is constituted so that, with the solenoid valve 16, the supply of operating oil 18 is effected by the plate 22 and pin 23 pushing downward on the ball 24 when the coil 21 is in energized state, and the supply of operating oil 18 is blocked by the ball 24 being pushed upward by the spring 25 when the coil is in an unenergized state, and also so that, through the use of the control valve 17, the spool 26 is pushed upward by oil pressure when the solenoid valve 16 is in an open state and the transport of operating oil 18 is effected only in the direction of the above-mentioned oil line 13 due to a ball 27 provided inside the said spool 26, and oil pressure is released toward the relief outlet 29 by the spool 26 being pushed downward by the spring 28 when the solenoid valve 16 is in a closed state.
FIG. 2 illustrates a design configuration for multiple cylinders exemplified in the case of a tandem 6-cylinder engine. Only Cylinder #1 (1), Cylinder #2 (1), and Cylinder #3 (1) are depicted, and they are constituted such that the opening action of the exhaust valve 4 in proximity to top dead center compression in Cylinder #1 (1) is taken by the exhaust push rod 6 of Cylinder #3 (1), the opening action of the exhaust valve 4 in proximity to top dead center compression in Cylinder #2 (1) is taken by the exhaust push rod 6 of Cylinder #1 (1), the opening action of the exhaust valve 4 in proximity to top dead center compression in Cylinder #3 (1) is taken by the exhaust push rod 6 of Cylinder #2 (1). More specifically, they are arranged so that the exhaust valve 4 on one side can be opened in proximity to top dead center compression by driving the slave piston 14 of each cylinder with the use of the oil line 13 by means of the action of the master piston 12 using the exhaust rocker arm 7 (not shown in FIG. 2) on the basis of the exhaust push rod 6 of each cylinder.
Furthermore, as 9 in the diagram is an inlet push rod and 10 is an intake valve, it is needless to say that the said intake valve 10 is opened by means of an intake rocker arm (not shown) which is moved at an angle by the inlet push rod 9 during an intake stroke.
Therefore, as the control valve 17 functions as a check valve and closes the oil line 13 if the solenoid valve 16 is opened by a control signal 20 from the control device 19, in the event that Cylinder #1 (1), Cylinder #2 (1), and Cylinder #3 (1), respectively, reach proximity to the pressure top dead center with a different timing, as is indicated in Diagram 3, the master piston 12 is pushed downward by the exhaust rocker arm 7 with an upward thrust of the exhaust push rod 6 for the purpose of opening an exhaust valve 4 in a separate cylinder during an exhaust stroke, thus creating pressure in the oil line 13. Since the slave piston 14 of the cylinder 1 in proximity to the pressure top dead center is driven and an exhaust valve 4 on one side is opened, compressed air from the combustion chamber 2 escapes into the exhaust port 5 and the creation of capacity to push the piston 3 downward during the next expansion stroke is lost, thus making it possible to take effective advantage of the braking capacity achieved in the compression stroke.
Moreover, in FIG. 3 (identical for FIG. 9 and FIG. 11, to be referenced later), the vertical axis represents lift (lifting range) and the horizontal axis represents the angle of rotation of the camshaft in Cylinder #1, while the xe2x80x9cxcex94xe2x80x9d figures in the diagram indicate top dead center compression in each cylinder, the curves in the solid lines indicate lift in the exhaust valve 4 in each cylinder, and the curves in the dotted lines indicate the lift in the intake valve 10 (in Cylinder #1, for example, a 0xc2x0xcx9c180xc2x0 angle of rotation of the camshaft constitutes a explosive stroke,180xc2x0xcx9c360xc2x0 an exhaust stroke, 360xc2x0xcx9c540xc2x0 an intake stroke, and 540xc2x0xcx9c720xc2x0 a compression stroke, while the phases are shifted with top dead center compression as the origin.)
If the solenoid valve 16 is closed by a control signal 20 from the control device 19, oil pressure in the oil line 13 is released by the control valve 17, and as pressure is not generated inside the oil line 13, the slave piston 14 ceases to be driven and the exhaust valve 4 is opened by normal valve opening operation only during an exhaust stroke and no longer is opened in proximity to top dead center compression.
In implementing the use of this compression pressure release form of engine braking, especially in the case of an OHV type engine as illustrated in FIG. 1, the actuator pin 15 is through mounted on the side of the cross head 8, facing in a vertical direction, and is configured in such a way that only an exhaust valve 4 on one side is opened by pushing the said actuator pin 15 downward with the slave piston 14, but there is a problem with opening up only an exhaust valve 4 on one side in that it is difficult to achieve greater engine braking capacity without being able to release pressure within the combustion chamber more effectively.
Namely, the exhaust rocker arm 7 in an OHV type engine is moved at an angle by linking it with the vertical reciprocating motion of the exhaust push rod 6 through the use of a camshaft not shown in the diagram, so, for example, the movements of the exhaust push rod 6 in proximity to top dead center compression are disregarded and the exhaust rocker arm 7 is moved at an angle by the slave piston 14, and as a result of this there are situations in which risk exists in that the linkage between the exhaust push rod 6 and exhaust rocker arm can end up being disconnected despite both exhaust valves 4 being opened, so the use of a structure in which the exhaust rocker arm 7 is not moved at an angle except during an exhaust stroke has been avoided.
The present invention is one which has been made with a view the aforementioned situation, and its object is to provide a valve opening mechanism which is designed in such a way that all engine valves that are opened by a rocker arm will be able to be opened separately without inclining a rocker arm.
The present invention is one that has been equipped with a rocker arm that activates to open by pushing the base extremity upward with a push rod and by pushing a engine valve downward with a tip at the time of its angular movement, and an actuator pin which is through mounted to slide freely facing in a vertical direction relative to the tip of the said rocker arm and fitted with a hook stop by which the bottom of the tip of the rocker arm is restrained at its designated top position, and which involves a valve opening mechanism characterized in that it has been constructed so as to enable the opening of engine valves by pushing downward on the said actuator pin during the exhaust stroke of the above-mentioned rocker arm.
However, if the actuator pin is pushed downward during a non-inclined motion of the rocker arm, the said actuator pin will slide in a downward direction against the tip of the rocker arm, and the engine valves will be opened, in an identical manner to that which occurs with a rocker arm, with the actuator pin being pushed downward to the same point as the tip of the rocker arm is being pushed down to during a normal valve opening operation.
Furthermore, when the rocker arm is moved at an angle by the push rod to perform a normal valve opening operation, the actuator pin is fixed in its designated top position due to the fact that a hook stop is held to the bottom of the tip of the rocker arm and, with the use of that fixed actuator pin, the engine valves are pushed downward and opened by the tip of the rocker arm.
It is additionally desirable in the present invention that the actuator pin is constituted by a pin base which, having an hook stop at its longitudinal direction midsection, and which is through-mounted to slide freely in the area above the said hook stop and faces in a vertical direction in relation to the tip of the rocker arm, is also formed in a spherical shape on its lower extremity, and by a tip which maintains contact with the spherically-shaped component on the lower extremity of the said pin base through the use of a spherical sheet and which has a flat tread that pushes downward on the engine valves beneath it.
If done this way, even if the pin base of the actuator pin is inclined by the angular movement of the rocker arm, the tip on its bottom oscillates reciprocally and the inclination of the above-mentioned pin base is permitted when the rocker arm is moved at an angle by the push rod to perform a normal valve opening operation. On this basis, the above-mentioned tip is kept in this very posture whereby it comes into satisfactory contact with the bottom of the flat tread surface that faces toward the engine valves, so as a result, a normal valve opening operation by means of a rocker arm can be reliably executed without any impediment through the use of an actuator pin that has been fixed in the top position.
It is further preferable in the present invention to provide a master piston that is set into motion by being thrown upward by the base extremity of the rocker arm, a slave piston that pushes downward on the actuator pin at the end of the rocker arm provided in the appropriate cylinder whenever it is connected to the said master piston through the use of an oil line and pressure is generated in the said oil line by the operation of the above-mentioned master piston, and a means of supplying operating oil that switches back and forth to sustain or release oil pressure in the above-mentioned oil line.
Therefore, if oil pressure in the oil line is sustained by a means of supplying operating oil, the master piston is thrown upwards by the base extremity of the said rocker arm and operates whenever the rocker arm is moved at an angle by the push rod. As a result of this, the slave piston is driven by the generation of oil pressure in the oil line, and the engine valves are opened by the downward push of the actuator pin on the end of a rocker arm provided in the appropriate cylinder.
Moreover, pressure is not generated inside the oil line if oil pressure in the oil line is released by a means of supplying operating oil, and thus the slave piston ceases to be driven even if the master piston is moved, only normal valve opening operation is accomplished by the rocker arm, and valve opening operation by the actuator pin ceases to be performed.